Sean Baker Photo wrote: FWIW, I think that this article is the basis for how NiK are able to make TC operate so quickly. Not surprisingly, it was written by one of Kai's original gurus. The technique is patented, so direct duplication is out for the time being. I've emailed the author asking whether he's licensed any direction implementations which are available for download / purchase - I'll let you know if / when I hear something.

Not sure if you ever heard back from Ben, but I wrote him about this and he replied:

Hi Kurt,

Yes, that's my paper. My fast bilateral implementation has been licensed exclusively by a third party (not Nik), but the basic idea is used in a lot of places now. Take a look at the retouch tools in Aperture / iPhoto, for instance. The choice of separation filter (e.g. Median / Gaussian / Bilateral / Diffusion) can make a big difference in the quality of the results, as well as additional "smart" processing to avoid fuzzing edges, for instance.

Image processing + freediving, small world indeed!

Cheers,
Ben

I do not use Aperture nor iPhoto (and not too keen on jumping into yet more image processing software!). Maybe someone who does can share anything notable.

His mention about it being a "small world" was in response to the fact that I actually know this guy! We share a passion for the sport of freediving, but I had no idea he had anything to do with image processing. But I knew he worked in computer science, so when I saw his name mentioned here I thought I'd look him up on Facebook and ask. I told him I'm gonna' be picking his brain next time I see him!

Wow, I've just spent the last few hours reading this thread top to tail. I know I'm a couple of years late to the party but after a few inital tries I can see this is going to revolutionise my workflow!

Thanks so much to those involved, particularly Photons 2 Pixels and Sean, who have both put so much great info and time into this thread. I can see you're both still patiently replying to those who can't grasp the basic principle, which takes the patience of a saint when it's been gone over 100 times on this thread!

Again - thanks a million. This is the best retouching thread I've ever encountered on the net by a long chalk.

Harry Duns wrote: Wow, I've just spent the last few hours reading this thread top to tail. I know I'm a couple of years late to the party but after a few inital tries I can see this is going to revolutionise my workflow!

Thanks so much to those involved, particularly Photons 2 Pixels and Sean, who have both put so much great info and time into this thread. I can see you're both still patiently replying to those who can't grasp the basic principle, which takes the patience of a saint when it's been gone over 100 times on this thread!

Again - thanks a million. This is the best retouching thread I've ever encountered on the net by a long chalk.

If you have any questions, the best way to get me is to send me a message. I don't frequent the forums very often anymore.

Photons 2 Pixels Images wrote: If you have any questions, the best way to get me is to send me a message. I don't frequent the forums very often anymore.

That's kind of you but I 'get it' and everything I need to know has been covered in the huge number of previous posts Am now busy re-editing old pics with this concept - it's such a powerful technique!

I do not use Aperture nor iPhoto (and not too keen on jumping into yet more image processing software!). Maybe someone who does can share anything notable.

Brilliant! Thanks for sharing that with us - I'd gotten a reply from him (he is an incredibly gracious guy), but with far fewer details than would have made for an informative post [it probably helps that you know him!]. It's crazy the way that paths can cross like that.

Then, can you do the same, substract high pass from original, to get the low pass?

(x-z)/2 + 128 => this is not equal to y !

The reason I've got this question: by intuition, I thought low-passed portion and high-passed portion should be "symmetric", the sum of these two parts is the orginal, then these two should be commutative. But the blending mode of "linear light" indicates that the order of those two layers matters.

I just don't understand how come these two parts are not "symmetric". Why?

BTW, really appreciate your post, really like to see what's really happening behind the "art" part. That's also a reason I'm having that question :-)

Somewhere in this thread, pretty sure it was in here and not one of the treads that branched off from it, was a discussion of separating into Luminosity, Color and Detail. I was playing with it for a while and then stopped and would like to play with it again as I have a few images with real shiny models who I think I could more reliably rebuild the skin color using that method...

Anyone know where in this thread that is or if it was a different thread altogether?

Hi
First of all, I would like to thank all the recurrent contributors to this thread. This seems to me to be the place with the biggest concentration of ready to use information on the subject. Once again thanks (all the way from the French West Indies)

I however have a question. Once I take a year or two to wrap my head around the math involved and mastered the different layer styles and the calculations I might get it myself, but now, I am deeply in need of help.

I've a couple of times an image to explain spatial frequencies where a square that looks like the cloud filter + some noise is separated in 6 frequencies.
How can I do that with an image, in other words how can I separate an image in 3, 4 or more frequencies. I've tried to refer engineer it, but can't seem to find the proper Apply Image values or/and layer blend modes.

split the image as described for a very narrow frequency; say, one pixel. Then split the low-frequency layer for a higher value, like 4 px. then split the low one again, for a higher value, like 10px. repeat as desired.

I used to do this, but found that I was having to fix the same thing on at least 2 layers, so i dropped back to one split.

it might also work to do the opposite; split for the highest value, and then split the high frequency layer for the next lowest value and repeat that way. try both and see which produces which results.

As much as I admire the technical knowledge behind the math, I do not think its mandatory to know this info to achieve the result you are looking for. Photography and Sharpening are subjective. One can easily complicate anything they choose, or simplify a process to meet their needs. Some responses here are very valid and show users how to over-think what should or could be a very simple approach.

FS is an often used term and technique, primarily used in cosmetic work to split frequencies. Its inventive to use it as a method to sharpening. In all honestly I have tried these techniques on files of all sizes and find no added value to them over the simplest method of HP for sharpening.

If HP is done correctly with selective choosing, its as good as it gets. HP is really just an action of FS anyways. If you use it in moderation for the tones you seek to enhance, and eliminate it where its not needed, that serves my purposes.

IE: stamp your image and apply a .5 HP and set to VL or LL and boom, a very nice way to enhance Specular HL's. Or apply a 2 HP and set to SL or OL and you get another range of tones being sharpened. *These settings are of course relative to the size of your file.

Because there are 2 methods, based on whether you are in 8-bit vs 16bit, what happens to your HP layer(s) if you started in 16-bit and converted to 8-bit? or vice versa?

There are those that will tell you you're risking a life in hell for all the destruction that move will create in your files, and there are people like me, that will tell you the net effect is so small as to hardly be noticeable. About the only time I've seen a benefit to using 16 bit files is when banding in vignettes is an issue. You can also crank on a curve a bit harder in 16 bit before the file disintegrates, but most of my work doesn't require such heavy hands.

Robert Randall wrote: There are those that will tell you you're risking a life in hell for all the destruction that move will create in your files, and there are people like me, that will tell you the net effect is so small as to hardly be noticeable. About the only time I've seen a benefit to using 16 bit files is when banding in vignettes is an issue. You can also crank on a curve a bit harder in 16 bit before the file disintegrates, but most of my work doesn't require such heavy hands.

I would probably never see a change between 8 and 16-bit... not too worried about that. What I was wondering more was, would I have to recreate the 16-bit HF layer using the 8-bit method? or once the layer was made, converting down to 8-bit won't harm the layer and I can continue using the same HF layer like nothing changed.

I would probably never see a change between 8 and 16-bit... not too worried about that. What I was wondering more was, would I have to recreate the 16-bit HF layer using the 8-bit method? or once the layer was made, converting down to 8-bit won't harm the layer and I can continue using the same HF layer like nothing changed.

Like I said, unless you see visible artifact, which I doubt you will, there should be no down side. Again, there will be those that think I'm nuts. I assume most of those folks have 30X40 prints hanging at Fahey Klein next to the Herb Ritts display.

Ya my main fear was more with the HF layer, and how making the layer differs between an 8-bit image and a 16-bit image... wasn't sure if dropping the image down to 8-bit messes up that layer or once it's been made, it doesn't matter.

I'm just practising with an image I got off the retouch section of the forums here, using a few new methods for the skin retouch and using the curves for dodge and burn.... but soon realized my file was 540mb and chugging along very very slowly. Switching to 8-bit dropped it down to 325mb.

THRobinson wrote: Ya my main fear was more with the HF layer, and how making the layer differs between an 8-bit image and a 16-bit image... wasn't sure if dropping the image down to 8-bit messes up that layer or once it's been made, it doesn't matter.

I'm just practising with an image I got off the retouch section of the forums here, using a few new methods for the skin retouch and using the curves for dodge and burn.... but soon realized my file was 540mb and chugging along very very slowly. Switching to 8-bit dropped it down to 325mb.

Older PC, kinda miss my MAC for this stuff.

I sometimes have to work for art directors that insist, as a final product, that I supply a complete layered file in 16 bit. I'm working on one right now that is closing in on 4GB. Stupid!

I'm kind of concerned by some results I'm seeing in the 8-bit process. I wonder if I'm doing it wrong?

The image below links to a crop of a layered PSD. The original layer is straight from lightroom. The image has been split twice, once for noise and once for detail (and then stacked up with linear light). I see basically zero detail in the (admittedly noisy) shadows.

By contrast, in 16bit, I detect no difference whatsoever, and have to really crank a curve on a difference layer to see any change at all.

I know the 16 bit process is more "accurate" but are my results typical?

THRobinson wrote: my main fear was more with the HF layer, and how making the layer differs between an 8-bit image and a 16-bit image... wasn't sure if dropping the image down to 8-bit messes up that layer or once it's been made, it doesn't matter.

I see a definite brightness shift when I convert a 16bit layered and separated file down to 8 bit.

pity I forgot this issue when I went through some of my old edited files and downsampled them to 8-bit to make some emergency room on the hard drive.